How to design a small coop for winter?

So winter is coming and I want to build a coop instead of buying one. I got some woods and their garbage woods that the construction workers don't need and throw away after done building a house. But I saw that the woods are still pretty useful. And I want to make like a simple coop and I don't need to put a nesting box their. Is just a SMALL coop for winter and in the spring through fall, I don't need to use the coop until winter. So it will be like a small barn coop kinda like coop. I have three hens.

The most important things to keep in mind when building a shelter for cold weather is ventilation. Damp air will cause condensation, which can cause frostbite. An sloped roof, that's higher on one side than the other, with plenty of vent holes near the roofline on the low side wall and the high side wall will provide the most effective ventilation. You will also need to make sure the roosting bars are at least 4 inches wide, so they can keep their feet completely covered while roosting.